i2c: add support for Socionext SynQuacer I2C controller
authorArd Biesheuvel <ard.biesheuvel@linaro.org>
Tue, 3 Apr 2018 19:11:49 +0000 (21:11 +0200)
committerWolfram Sang <wsa@the-dreams.de>
Wed, 4 Apr 2018 18:33:03 +0000 (20:33 +0200)
This is a cleaned up version of the I2C controller driver for
the Fujitsu F_I2C IP, which was never supported upstream, and
has now been incorporated into the Socionext SynQuacer SoC.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
[wsa: updated MAINTAINERS entry and removed two empty lines]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
MAINTAINERS
drivers/i2c/busses/Kconfig
drivers/i2c/busses/Makefile
drivers/i2c/busses/i2c-synquacer.c [new file with mode: 0644]

index 2d3f847cdc8dc35081b54f7e6dc8205f78eb02ad..284867be62c5312ea197467b01dc559c709a50db 100644 (file)
@@ -12816,6 +12816,13 @@ F:     include/media/soc*
 F:     drivers/media/i2c/soc_camera/
 F:     drivers/media/platform/soc_camera/
 
+SOCIONEXT SYNQUACER I2C DRIVER
+M:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
+L:     linux-i2c@vger.kernel.org
+S:     Maintained
+F:     drivers/i2c/busses/i2c-synquacer.c
+F:     Documentation/devicetree/bindings/i2c/i2c-synquacer.txt
+
 SOCIONEXT UNIPHIER SOUND DRIVER
 M:     Katsuhiro Suzuki <suzuki.katsuhiro@socionext.com>
 L:     alsa-devel@alsa-project.org (moderated for non-subscribers)
index e2954fb86d659f366a250ab65640ed2e0ad002ec..56903952d364fc93ba10ee8f63f9746cfed07afe 100644 (file)
@@ -997,6 +997,16 @@ config I2C_SUN6I_P2WI
          This interface is used to connect to specific PMIC devices (like the
          AXP221).
 
+config I2C_SYNQUACER
+       tristate "Socionext SynQuacer I2C controller"
+       depends on ARCH_SYNQUACER || COMPILE_TEST
+       help
+         Say Y here to include support for the I2C controller used in some
+         Fujitsu and Socionext SoCs.
+
+         This driver can also be built as a module. If so, the module
+         will be called i2c-synquacer.
+
 config I2C_TEGRA
        tristate "NVIDIA Tegra internal I2C controller"
        depends on ARCH_TEGRA
index 2ce8576540a29a4abf80f4ca2767d9ca6448939d..40ab7bfc345853ddb8895af378b4aa764e510f12 100644 (file)
@@ -98,6 +98,7 @@ obj-$(CONFIG_I2C_STM32F4)     += i2c-stm32f4.o
 obj-$(CONFIG_I2C_STM32F7)      += i2c-stm32f7.o
 obj-$(CONFIG_I2C_STU300)       += i2c-stu300.o
 obj-$(CONFIG_I2C_SUN6I_P2WI)   += i2c-sun6i-p2wi.o
+obj-$(CONFIG_I2C_SYNQUACER)    += i2c-synquacer.o
 obj-$(CONFIG_I2C_TEGRA)                += i2c-tegra.o
 obj-$(CONFIG_I2C_TEGRA_BPMP)   += i2c-tegra-bpmp.o
 obj-$(CONFIG_I2C_UNIPHIER)     += i2c-uniphier.o
diff --git a/drivers/i2c/busses/i2c-synquacer.c b/drivers/i2c/busses/i2c-synquacer.c
new file mode 100644 (file)
index 0000000..a021f86
--- /dev/null
@@ -0,0 +1,667 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012 FUJITSU SEMICONDUCTOR LIMITED
+ */
+
+#include <linux/acpi.h>
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+
+#define WAIT_PCLK(n, rate)     \
+       ndelay(DIV_ROUND_UP(DIV_ROUND_UP(1000000000, rate), n) + 10)
+
+/* I2C register address definitions */
+#define SYNQUACER_I2C_REG_BSR          (0x00 << 2) // Bus Status
+#define SYNQUACER_I2C_REG_BCR          (0x01 << 2) // Bus Control
+#define SYNQUACER_I2C_REG_CCR          (0x02 << 2) // Clock Control
+#define SYNQUACER_I2C_REG_ADR          (0x03 << 2) // Address
+#define SYNQUACER_I2C_REG_DAR          (0x04 << 2) // Data
+#define SYNQUACER_I2C_REG_CSR          (0x05 << 2) // Expansion CS
+#define SYNQUACER_I2C_REG_FSR          (0x06 << 2) // Bus Clock Freq
+#define SYNQUACER_I2C_REG_BC2R         (0x07 << 2) // Bus Control 2
+
+/* I2C register bit definitions */
+#define SYNQUACER_I2C_BSR_FBT          BIT(0)  // First Byte Transfer
+#define SYNQUACER_I2C_BSR_GCA          BIT(1)  // General Call Address
+#define SYNQUACER_I2C_BSR_AAS          BIT(2)  // Address as Slave
+#define SYNQUACER_I2C_BSR_TRX          BIT(3)  // Transfer/Receive
+#define SYNQUACER_I2C_BSR_LRB          BIT(4)  // Last Received Bit
+#define SYNQUACER_I2C_BSR_AL           BIT(5)  // Arbitration Lost
+#define SYNQUACER_I2C_BSR_RSC          BIT(6)  // Repeated Start Cond.
+#define SYNQUACER_I2C_BSR_BB           BIT(7)  // Bus Busy
+
+#define SYNQUACER_I2C_BCR_INT          BIT(0)  // Interrupt
+#define SYNQUACER_I2C_BCR_INTE         BIT(1)  // Interrupt Enable
+#define SYNQUACER_I2C_BCR_GCAA         BIT(2)  // Gen. Call Access Ack.
+#define SYNQUACER_I2C_BCR_ACK          BIT(3)  // Acknowledge
+#define SYNQUACER_I2C_BCR_MSS          BIT(4)  // Master Slave Select
+#define SYNQUACER_I2C_BCR_SCC          BIT(5)  // Start Condition Cont.
+#define SYNQUACER_I2C_BCR_BEIE         BIT(6)  // Bus Error Int Enable
+#define SYNQUACER_I2C_BCR_BER          BIT(7)  // Bus Error
+
+#define SYNQUACER_I2C_CCR_CS_MASK      (0x1f)  // CCR Clock Period Sel.
+#define SYNQUACER_I2C_CCR_EN           BIT(5)  // Enable
+#define SYNQUACER_I2C_CCR_FM           BIT(6)  // Speed Mode Select
+
+#define SYNQUACER_I2C_CSR_CS_MASK      (0x3f)  // CSR Clock Period Sel.
+
+#define SYNQUACER_I2C_BC2R_SCLL                BIT(0)  // SCL Low Drive
+#define SYNQUACER_I2C_BC2R_SDAL                BIT(1)  // SDA Low Drive
+#define SYNQUACER_I2C_BC2R_SCLS                BIT(4)  // SCL Status
+#define SYNQUACER_I2C_BC2R_SDAS                BIT(5)  // SDA Status
+
+/* PCLK frequency */
+#define SYNQUACER_I2C_BUS_CLK_FR(rate) (((rate) / 20000000) + 1)
+
+/* STANDARD MODE frequency */
+#define SYNQUACER_I2C_CLK_MASTER_STD(rate)                     \
+       DIV_ROUND_UP(DIV_ROUND_UP((rate), 100000) - 2, 2)
+/* FAST MODE frequency */
+#define SYNQUACER_I2C_CLK_MASTER_FAST(rate)                    \
+       DIV_ROUND_UP((DIV_ROUND_UP((rate), 400000) - 2) * 2, 3)
+
+/* (clkrate <= 18000000) */
+/* calculate the value of CS bits in CCR register on standard mode */
+#define SYNQUACER_I2C_CCR_CS_STD_MAX_18M(rate)                 \
+          ((SYNQUACER_I2C_CLK_MASTER_STD(rate) - 65)           \
+                                       & SYNQUACER_I2C_CCR_CS_MASK)
+
+/* calculate the value of CS bits in CSR register on standard mode */
+#define SYNQUACER_I2C_CSR_CS_STD_MAX_18M(rate)         0x00
+
+/* calculate the value of CS bits in CCR register on fast mode */
+#define SYNQUACER_I2C_CCR_CS_FAST_MAX_18M(rate)                        \
+          ((SYNQUACER_I2C_CLK_MASTER_FAST(rate) - 1)           \
+                                       & SYNQUACER_I2C_CCR_CS_MASK)
+
+/* calculate the value of CS bits in CSR register on fast mode */
+#define SYNQUACER_I2C_CSR_CS_FAST_MAX_18M(rate)                0x00
+
+/* (clkrate > 18000000) */
+/* calculate the value of CS bits in CCR register on standard mode */
+#define SYNQUACER_I2C_CCR_CS_STD_MIN_18M(rate)                 \
+          ((SYNQUACER_I2C_CLK_MASTER_STD(rate) - 1)            \
+                                       & SYNQUACER_I2C_CCR_CS_MASK)
+
+/* calculate the value of CS bits in CSR register on standard mode */
+#define SYNQUACER_I2C_CSR_CS_STD_MIN_18M(rate)                 \
+          (((SYNQUACER_I2C_CLK_MASTER_STD(rate) - 1) >> 5)     \
+                                       & SYNQUACER_I2C_CSR_CS_MASK)
+
+/* calculate the value of CS bits in CCR register on fast mode */
+#define SYNQUACER_I2C_CCR_CS_FAST_MIN_18M(rate)                        \
+          ((SYNQUACER_I2C_CLK_MASTER_FAST(rate) - 1)           \
+                                       & SYNQUACER_I2C_CCR_CS_MASK)
+
+/* calculate the value of CS bits in CSR register on fast mode */
+#define SYNQUACER_I2C_CSR_CS_FAST_MIN_18M(rate)                        \
+          (((SYNQUACER_I2C_CLK_MASTER_FAST(rate) - 1) >> 5)    \
+                                       & SYNQUACER_I2C_CSR_CS_MASK)
+
+/* min I2C clock frequency 14M */
+#define SYNQUACER_I2C_MIN_CLK_RATE     (14 * 1000000)
+/* max I2C clock frequency 200M */
+#define SYNQUACER_I2C_MAX_CLK_RATE     (200 * 1000000)
+/* I2C clock frequency 18M */
+#define SYNQUACER_I2C_CLK_RATE_18M     (18 * 1000000)
+
+#define SYNQUACER_I2C_SPEED_FM         400     // Fast Mode
+#define SYNQUACER_I2C_SPEED_SM         100     // Standard Mode
+
+enum i2c_state {
+       STATE_IDLE,
+       STATE_START,
+       STATE_READ,
+       STATE_WRITE
+};
+
+struct synquacer_i2c {
+       struct completion       completion;
+
+       struct i2c_msg          *msg;
+       u32                     msg_num;
+       u32                     msg_idx;
+       u32                     msg_ptr;
+
+       int                     irq;
+       struct device           *dev;
+       void __iomem            *base;
+       struct clk              *pclk;
+       u32                     pclkrate;
+       u32                     speed_khz;
+       u32                     timeout_ms;
+       enum i2c_state          state;
+       struct i2c_adapter      adapter;
+
+       bool                    is_suspended;
+};
+
+static inline int is_lastmsg(struct synquacer_i2c *i2c)
+{
+       return i2c->msg_idx >= (i2c->msg_num - 1);
+}
+
+static inline int is_msglast(struct synquacer_i2c *i2c)
+{
+       return i2c->msg_ptr == (i2c->msg->len - 1);
+}
+
+static inline int is_msgend(struct synquacer_i2c *i2c)
+{
+       return i2c->msg_ptr >= i2c->msg->len;
+}
+
+static inline unsigned long calc_timeout_ms(struct synquacer_i2c *i2c,
+                                           struct i2c_msg *msgs,
+                                           int num)
+{
+       unsigned long bit_count = 0;
+       int i;
+
+       for (i = 0; i < num; i++, msgs++)
+               bit_count += msgs->len;
+
+       return DIV_ROUND_UP((bit_count * 9 + num * 10) * 3, 200) + 10;
+}
+
+static void synquacer_i2c_stop(struct synquacer_i2c *i2c, int ret)
+{
+       /*
+        * clear IRQ (INT=0, BER=0)
+        * set Stop Condition (MSS=0)
+        * Interrupt Disable
+        */
+       writeb(0, i2c->base + SYNQUACER_I2C_REG_BCR);
+
+       i2c->state = STATE_IDLE;
+
+       i2c->msg_ptr = 0;
+       i2c->msg = NULL;
+       i2c->msg_idx++;
+       i2c->msg_num = 0;
+       if (ret)
+               i2c->msg_idx = ret;
+
+       complete(&i2c->completion);
+}
+
+static void synquacer_i2c_hw_init(struct synquacer_i2c *i2c)
+{
+       unsigned char ccr_cs, csr_cs;
+       u32 rt = i2c->pclkrate;
+
+       /* Set own Address */
+       writeb(0, i2c->base + SYNQUACER_I2C_REG_ADR);
+
+       /* Set PCLK frequency */
+       writeb(SYNQUACER_I2C_BUS_CLK_FR(i2c->pclkrate),
+              i2c->base + SYNQUACER_I2C_REG_FSR);
+
+       switch (i2c->speed_khz) {
+       case SYNQUACER_I2C_SPEED_FM:
+               if (i2c->pclkrate <= SYNQUACER_I2C_CLK_RATE_18M) {
+                       ccr_cs = SYNQUACER_I2C_CCR_CS_FAST_MAX_18M(rt);
+                       csr_cs = SYNQUACER_I2C_CSR_CS_FAST_MAX_18M(rt);
+               } else {
+                       ccr_cs = SYNQUACER_I2C_CCR_CS_FAST_MIN_18M(rt);
+                       csr_cs = SYNQUACER_I2C_CSR_CS_FAST_MIN_18M(rt);
+               }
+
+               /* Set Clock and enable, Set fast mode */
+               writeb(ccr_cs | SYNQUACER_I2C_CCR_FM |
+                      SYNQUACER_I2C_CCR_EN,
+                      i2c->base + SYNQUACER_I2C_REG_CCR);
+               writeb(csr_cs, i2c->base + SYNQUACER_I2C_REG_CSR);
+               break;
+       case SYNQUACER_I2C_SPEED_SM:
+               if (i2c->pclkrate <= SYNQUACER_I2C_CLK_RATE_18M) {
+                       ccr_cs = SYNQUACER_I2C_CCR_CS_STD_MAX_18M(rt);
+                       csr_cs = SYNQUACER_I2C_CSR_CS_STD_MAX_18M(rt);
+               } else {
+                       ccr_cs = SYNQUACER_I2C_CCR_CS_STD_MIN_18M(rt);
+                       csr_cs = SYNQUACER_I2C_CSR_CS_STD_MIN_18M(rt);
+               }
+
+               /* Set Clock and enable, Set standard mode */
+               writeb(ccr_cs | SYNQUACER_I2C_CCR_EN,
+                     i2c->base + SYNQUACER_I2C_REG_CCR);
+               writeb(csr_cs, i2c->base + SYNQUACER_I2C_REG_CSR);
+               break;
+       default:
+               WARN_ON(1);
+       }
+
+       /* clear IRQ (INT=0, BER=0), Interrupt Disable */
+       writeb(0, i2c->base + SYNQUACER_I2C_REG_BCR);
+       writeb(0, i2c->base + SYNQUACER_I2C_REG_BC2R);
+}
+
+static void synquacer_i2c_hw_reset(struct synquacer_i2c *i2c)
+{
+       /* Disable clock */
+       writeb(0, i2c->base + SYNQUACER_I2C_REG_CCR);
+       writeb(0, i2c->base + SYNQUACER_I2C_REG_CSR);
+
+       WAIT_PCLK(100, i2c->pclkrate);
+}
+
+static int synquacer_i2c_master_start(struct synquacer_i2c *i2c,
+                                     struct i2c_msg *pmsg)
+{
+       unsigned char bsr, bcr;
+
+       writeb(i2c_8bit_addr_from_msg(pmsg), i2c->base + SYNQUACER_I2C_REG_DAR);
+
+       dev_dbg(i2c->dev, "slave:0x%02x\n", pmsg->addr);
+
+       /* Generate Start Condition */
+       bsr = readb(i2c->base + SYNQUACER_I2C_REG_BSR);
+       bcr = readb(i2c->base + SYNQUACER_I2C_REG_BCR);
+       dev_dbg(i2c->dev, "bsr:0x%02x, bcr:0x%02x\n", bsr, bcr);
+
+       if ((bsr & SYNQUACER_I2C_BSR_BB) &&
+           !(bcr & SYNQUACER_I2C_BCR_MSS)) {
+               dev_dbg(i2c->dev, "bus is busy");
+               return -EBUSY;
+       }
+
+       if (bsr & SYNQUACER_I2C_BSR_BB) { /* Bus is busy */
+               dev_dbg(i2c->dev, "Continuous Start");
+               writeb(bcr | SYNQUACER_I2C_BCR_SCC,
+                      i2c->base + SYNQUACER_I2C_REG_BCR);
+       } else {
+               if (bcr & SYNQUACER_I2C_BCR_MSS) {
+                       dev_dbg(i2c->dev, "not in master mode");
+                       return -EAGAIN;
+               }
+               dev_dbg(i2c->dev, "Start Condition");
+               /* Start Condition + Enable Interrupts */
+               writeb(bcr | SYNQUACER_I2C_BCR_MSS |
+                      SYNQUACER_I2C_BCR_INTE | SYNQUACER_I2C_BCR_BEIE,
+                      i2c->base + SYNQUACER_I2C_REG_BCR);
+       }
+
+       WAIT_PCLK(10, i2c->pclkrate);
+
+       /* get BSR & BCR registers */
+       bsr = readb(i2c->base + SYNQUACER_I2C_REG_BSR);
+       bcr = readb(i2c->base + SYNQUACER_I2C_REG_BCR);
+       dev_dbg(i2c->dev, "bsr:0x%02x, bcr:0x%02x\n", bsr, bcr);
+
+       if ((bsr & SYNQUACER_I2C_BSR_AL) ||
+           !(bcr & SYNQUACER_I2C_BCR_MSS)) {
+               dev_dbg(i2c->dev, "arbitration lost\n");
+               return -EAGAIN;
+       }
+
+       return 0;
+}
+
+static int synquacer_i2c_doxfer(struct synquacer_i2c *i2c,
+                               struct i2c_msg *msgs, int num)
+{
+       unsigned char bsr;
+       unsigned long timeout;
+       int ret;
+
+       if (i2c->is_suspended)
+               return -EBUSY;
+
+       synquacer_i2c_hw_init(i2c);
+       bsr = readb(i2c->base + SYNQUACER_I2C_REG_BSR);
+       if (bsr & SYNQUACER_I2C_BSR_BB) {
+               dev_err(i2c->dev, "cannot get bus (bus busy)\n");
+               return -EBUSY;
+       }
+
+       reinit_completion(&i2c->completion);
+
+       i2c->msg = msgs;
+       i2c->msg_num = num;
+       i2c->msg_ptr = 0;
+       i2c->msg_idx = 0;
+       i2c->state = STATE_START;
+
+       ret = synquacer_i2c_master_start(i2c, i2c->msg);
+       if (ret < 0) {
+               dev_dbg(i2c->dev, "Address failed: (%d)\n", ret);
+               return ret;
+       }
+
+       timeout = wait_for_completion_timeout(&i2c->completion,
+                                       msecs_to_jiffies(i2c->timeout_ms));
+       if (timeout == 0) {
+               dev_dbg(i2c->dev, "timeout\n");
+               return -EAGAIN;
+       }
+
+       ret = i2c->msg_idx;
+       if (ret != num) {
+               dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);
+               return -EAGAIN;
+       }
+
+       /* wait 2 clock periods to ensure the stop has been through the bus */
+       udelay(DIV_ROUND_UP(2 * 1000, i2c->speed_khz));
+
+       return 0;
+}
+
+static irqreturn_t synquacer_i2c_isr(int irq, void *dev_id)
+{
+       struct synquacer_i2c *i2c = dev_id;
+
+       unsigned char byte;
+       unsigned char bsr, bcr;
+       int ret;
+
+       bcr = readb(i2c->base + SYNQUACER_I2C_REG_BCR);
+       bsr = readb(i2c->base + SYNQUACER_I2C_REG_BSR);
+       dev_dbg(i2c->dev, "bsr:0x%02x, bcr:0x%02x\n", bsr, bcr);
+
+       if (bcr & SYNQUACER_I2C_BCR_BER) {
+               dev_err(i2c->dev, "bus error\n");
+               synquacer_i2c_stop(i2c, -EAGAIN);
+               goto out;
+       }
+       if ((bsr & SYNQUACER_I2C_BSR_AL) ||
+           !(bcr & SYNQUACER_I2C_BCR_MSS)) {
+               dev_dbg(i2c->dev, "arbitration lost\n");
+               synquacer_i2c_stop(i2c, -EAGAIN);
+               goto out;
+       }
+
+       switch (i2c->state) {
+       case STATE_START:
+               if (bsr & SYNQUACER_I2C_BSR_LRB) {
+                       dev_dbg(i2c->dev, "ack was not received\n");
+                       synquacer_i2c_stop(i2c, -EAGAIN);
+                       goto out;
+               }
+
+               if (i2c->msg->flags & I2C_M_RD)
+                       i2c->state = STATE_READ;
+               else
+                       i2c->state = STATE_WRITE;
+
+               if (is_lastmsg(i2c) && i2c->msg->len == 0) {
+                       synquacer_i2c_stop(i2c, 0);
+                       goto out;
+               }
+
+               if (i2c->state == STATE_READ)
+                       goto prepare_read;
+
+               /* fallthru */
+
+       case STATE_WRITE:
+               if (bsr & SYNQUACER_I2C_BSR_LRB) {
+                       dev_dbg(i2c->dev, "WRITE: No Ack\n");
+                       synquacer_i2c_stop(i2c, -EAGAIN);
+                       goto out;
+               }
+
+               if (!is_msgend(i2c)) {
+                       writeb(i2c->msg->buf[i2c->msg_ptr++],
+                              i2c->base + SYNQUACER_I2C_REG_DAR);
+
+                       /* clear IRQ, and continue */
+                       writeb(SYNQUACER_I2C_BCR_BEIE |
+                              SYNQUACER_I2C_BCR_MSS |
+                              SYNQUACER_I2C_BCR_INTE,
+                              i2c->base + SYNQUACER_I2C_REG_BCR);
+                       break;
+               }
+               if (is_lastmsg(i2c)) {
+                       synquacer_i2c_stop(i2c, 0);
+                       break;
+               }
+               dev_dbg(i2c->dev, "WRITE: Next Message\n");
+
+               i2c->msg_ptr = 0;
+               i2c->msg_idx++;
+               i2c->msg++;
+
+               /* send the new start */
+               ret = synquacer_i2c_master_start(i2c, i2c->msg);
+               if (ret < 0) {
+                       dev_dbg(i2c->dev, "restart error (%d)\n", ret);
+                       synquacer_i2c_stop(i2c, -EAGAIN);
+                       break;
+               }
+               i2c->state = STATE_START;
+               break;
+
+       case STATE_READ:
+               byte = readb(i2c->base + SYNQUACER_I2C_REG_DAR);
+               if (!(bsr & SYNQUACER_I2C_BSR_FBT)) /* data */
+                       i2c->msg->buf[i2c->msg_ptr++] = byte;
+               else /* address */
+                       dev_dbg(i2c->dev, "address:0x%02x. ignore it.\n", byte);
+
+prepare_read:
+               if (is_msglast(i2c)) {
+                       writeb(SYNQUACER_I2C_BCR_MSS |
+                              SYNQUACER_I2C_BCR_BEIE |
+                              SYNQUACER_I2C_BCR_INTE,
+                              i2c->base + SYNQUACER_I2C_REG_BCR);
+                       break;
+               }
+               if (!is_msgend(i2c)) {
+                       writeb(SYNQUACER_I2C_BCR_MSS |
+                              SYNQUACER_I2C_BCR_BEIE |
+                              SYNQUACER_I2C_BCR_INTE |
+                              SYNQUACER_I2C_BCR_ACK,
+                              i2c->base + SYNQUACER_I2C_REG_BCR);
+                       break;
+               }
+               if (is_lastmsg(i2c)) {
+                       /* last message, send stop and complete */
+                       dev_dbg(i2c->dev, "READ: Send Stop\n");
+                       synquacer_i2c_stop(i2c, 0);
+                       break;
+               }
+               dev_dbg(i2c->dev, "READ: Next Transfer\n");
+
+               i2c->msg_ptr = 0;
+               i2c->msg_idx++;
+               i2c->msg++;
+
+               ret = synquacer_i2c_master_start(i2c, i2c->msg);
+               if (ret < 0) {
+                       dev_dbg(i2c->dev, "restart error (%d)\n", ret);
+                       synquacer_i2c_stop(i2c, -EAGAIN);
+               } else {
+                       i2c->state = STATE_START;
+               }
+               break;
+       default:
+               dev_err(i2c->dev, "called in err STATE (%d)\n", i2c->state);
+               break;
+       }
+
+out:
+       WAIT_PCLK(10, i2c->pclkrate);
+       return IRQ_HANDLED;
+}
+
+static int synquacer_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+                             int num)
+{
+       struct synquacer_i2c *i2c;
+       int retry;
+       int ret;
+
+       i2c = i2c_get_adapdata(adap);
+       i2c->timeout_ms = calc_timeout_ms(i2c, msgs, num);
+
+       dev_dbg(i2c->dev, "calculated timeout %d ms\n", i2c->timeout_ms);
+
+       for (retry = 0; retry < adap->retries; retry++) {
+               ret = synquacer_i2c_doxfer(i2c, msgs, num);
+               if (ret != -EAGAIN)
+                       return ret;
+
+               dev_dbg(i2c->dev, "Retrying transmission (%d)\n", retry);
+
+               synquacer_i2c_hw_reset(i2c);
+       }
+       return -EIO;
+}
+
+static u32 synquacer_i2c_functionality(struct i2c_adapter *adap)
+{
+       return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static const struct i2c_algorithm synquacer_i2c_algo = {
+       .master_xfer    = synquacer_i2c_xfer,
+       .functionality  = synquacer_i2c_functionality,
+};
+
+static struct i2c_adapter synquacer_i2c_ops = {
+       .owner          = THIS_MODULE,
+       .name           = "synquacer_i2c-adapter",
+       .algo           = &synquacer_i2c_algo,
+       .retries        = 5,
+};
+
+static int synquacer_i2c_probe(struct platform_device *pdev)
+{
+       struct synquacer_i2c *i2c;
+       struct resource *r;
+       u32 bus_speed;
+       int ret;
+
+       i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
+       if (!i2c)
+               return -ENOMEM;
+
+       bus_speed = i2c_acpi_find_bus_speed(&pdev->dev);
+       if (!bus_speed)
+               device_property_read_u32(&pdev->dev, "clock-frequency",
+                                        &bus_speed);
+
+       device_property_read_u32(&pdev->dev, "socionext,pclk-rate",
+                                &i2c->pclkrate);
+
+       i2c->pclk = devm_clk_get(&pdev->dev, "pclk");
+       if (IS_ERR(i2c->pclk) && PTR_ERR(i2c->pclk) == -EPROBE_DEFER)
+               return -EPROBE_DEFER;
+       if (!IS_ERR_OR_NULL(i2c->pclk)) {
+               dev_dbg(&pdev->dev, "clock source %p\n", i2c->pclk);
+
+               ret = clk_prepare_enable(i2c->pclk);
+               if (ret) {
+                       dev_err(&pdev->dev, "failed to enable clock (%d)\n",
+                               ret);
+                       return ret;
+               }
+               i2c->pclkrate = clk_get_rate(i2c->pclk);
+       }
+
+       if (i2c->pclkrate < SYNQUACER_I2C_MIN_CLK_RATE ||
+           i2c->pclkrate > SYNQUACER_I2C_MAX_CLK_RATE) {
+               dev_err(&pdev->dev, "PCLK missing or out of range (%d)\n",
+                       i2c->pclkrate);
+               return -EINVAL;
+       }
+
+       r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+       i2c->base = devm_ioremap_resource(&pdev->dev, r);
+       if (IS_ERR(i2c->base))
+               return PTR_ERR(i2c->base);
+
+       i2c->irq = platform_get_irq(pdev, 0);
+       if (i2c->irq < 0) {
+               dev_err(&pdev->dev, "no IRQ resource found\n");
+               return -ENODEV;
+       }
+
+       ret = devm_request_irq(&pdev->dev, i2c->irq, synquacer_i2c_isr,
+                              0, dev_name(&pdev->dev), i2c);
+       if (ret < 0) {
+               dev_err(&pdev->dev, "cannot claim IRQ %d\n", i2c->irq);
+               return ret;
+       }
+
+       i2c->state = STATE_IDLE;
+       i2c->dev = &pdev->dev;
+       i2c->adapter = synquacer_i2c_ops;
+       i2c_set_adapdata(&i2c->adapter, i2c);
+       i2c->adapter.dev.parent = &pdev->dev;
+       i2c->adapter.nr = pdev->id;
+       init_completion(&i2c->completion);
+
+       if (bus_speed < 400000)
+               i2c->speed_khz = SYNQUACER_I2C_SPEED_SM;
+       else
+               i2c->speed_khz = SYNQUACER_I2C_SPEED_FM;
+
+       synquacer_i2c_hw_init(i2c);
+
+       ret = i2c_add_numbered_adapter(&i2c->adapter);
+       if (ret) {
+               dev_err(&pdev->dev, "failed to add bus to i2c core\n");
+               return ret;
+       }
+
+       platform_set_drvdata(pdev, i2c);
+
+       dev_info(&pdev->dev, "%s: synquacer_i2c adapter\n",
+                dev_name(&i2c->adapter.dev));
+
+       return 0;
+}
+
+static int synquacer_i2c_remove(struct platform_device *pdev)
+{
+       struct synquacer_i2c *i2c = platform_get_drvdata(pdev);
+
+       i2c_del_adapter(&i2c->adapter);
+       if (!IS_ERR(i2c->pclk))
+               clk_disable_unprepare(i2c->pclk);
+
+       return 0;
+};
+
+static const struct of_device_id synquacer_i2c_dt_ids[] = {
+       { .compatible = "socionext,synquacer-i2c" },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, synquacer_i2c_dt_ids);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id synquacer_i2c_acpi_ids[] = {
+       { "SCX0003" },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(acpi, synquacer_i2c_acpi_ids);
+#endif
+
+static struct platform_driver synquacer_i2c_driver = {
+       .probe  = synquacer_i2c_probe,
+       .remove = synquacer_i2c_remove,
+       .driver = {
+               .name = "synquacer_i2c",
+               .of_match_table = of_match_ptr(synquacer_i2c_dt_ids),
+               .acpi_match_table = ACPI_PTR(synquacer_i2c_acpi_ids),
+       },
+};
+module_platform_driver(synquacer_i2c_driver);
+
+MODULE_AUTHOR("Fujitsu Semiconductor Ltd");
+MODULE_DESCRIPTION("Socionext SynQuacer I2C Driver");
+MODULE_LICENSE("GPL v2");